Various types of platforms have been suggested heretofore in the art for use as a bus boarder. One known in the art has a platform mounted on parallelogram arms on opposite sides which are tilted by a sprocket and chain drive for raising the platform from the ground and depositing it on the floor within the bus. This type of mechanism required substantial changes at the bus entrances including remounting the doors to swing outwardly rather than retaining them in their original swing-in position.